New approach for prediction of specific energy using sound levels produced during core drilling operations

ABSTRACT Specific energy (SE) is the energy required to excavate a unit volume of rock. It is a very important variable in the planning and designing of excavation projects, mining, and petroleum industry and depends on rock properties. This investigation reports about the prediction of SE, the effect of properties of rocks on SE, and the effect of operational variables on SE using sound levels created during the drilling process. Initially, SE was determined for all selected rock types and a correlation was developed between SE and physico-mechanical rock properties (PMRP) and operating variables. The developed prediction models were validated using determination coefficients (R2), the t-test, F-test, and performance predictions i.e. values account for (VAF), root mean square error (RMSE) and mean absolute percentage error (MAPE). For SE, the R2 values obtained a range from 75.58% to 78.76%, RMSE values obtained a range from 0.074411 to 0.578601, VAF values obtained a range from 72.826808 to 84.155813 and MAPE values obtained a range from 0.061218 to 2.321007 for selected rock samples and also, t and F values obtained below the tabulated values. Concerning SE’s relation to PMRP, it was observed that SE increased with increasing uniaxial compressive strength, Brazilian tensile strength, and dry density and decreased with increasing abrasivity. For PMRP, the R2 values obtained from 92.25%, 90.99%, 47.15%, 93.39%, corresponded to uniaxial compressive strength, Brazilian tensile strength, density, and abrasivity. Similarly, regarding SE’s relation with operational variables, it was observed that SE decreased with increasing drill bit diameters, penetration rates, and drill bit speed. The developed models can be served in the exploration and excavation projects for the prediction of specific energy.